expert type icon EXPERT

Sean L. Johnston

Radiologist

Dr. Sean Johnston is a radiologist practicing in Burbank, California. Dr. Johnston specializes in diagnosing and treating injuries and diseases using medical imaging techniques such as X-Rays, magnetic resonance imaging and computed tomography exams. These techniques offer accurate visibility to the inside of the patients body and help to detect otherwise hidden illnesses so that they can be treated quickly and efficiently.
Sean L. Johnston
  • Burbank, California
  • Mayo Clinic
  • Accepting new patients

What do the results mean from my CT scan?

A radiology report is designed for the referring physician to view in context of your entire medical history in order to give them key information for any treatment/therapy planning READ MORE
A radiology report is designed for the referring physician to view in context of your entire medical history in order to give them key information for any treatment/therapy planning or lifestyle modification. In general, these are not meant to be interpreted by non-physicians, as they tend to consult with Dr. Google and arrive at erroneous conclusions. This report is best discussed with the primary care physician that ordered it in the first place so they can best answer your question.

However, in brief, you have a small right ovarian cyst which is very common. It will be up to the referring to decide how to best monitor this.

The endometrium (a portion of the uterus which normally changes with your cycle) is most likely in a phase just prior to your cycle. This needs to be confirmed and perhaps monitored in another six weeks.

The structure in the left adnexa (near the left ovary) is indeterminant. It will be up to the referring to decide how to best monitor this.

A small amount of free fluid in the pelvis is normal for menstruating females.

Probably not the definitive answers that you are looking for, but again, radiology findings are a piece of the whole puzzle. The referring needs to assemble them. I recommend talking to them about this report at your earliest convenience. Best of luck.

How does a renal ultrasound work?

Ultrasound uses sonar technology from submarines to create an image of internal organs and structures on the computer screen for the radiologist to interpret. The test involves READ MORE
Ultrasound uses sonar technology from submarines to create an image of internal organs and structures on the computer screen for the radiologist to interpret. The test involves putting a sticky gel on the skin and placing a transducer (about the size of a fist) on the skin surface. The sonar waves are directed into the body. The test is painless, uses no radiation at all, and gives important information. Good test to look for obstruction and stones within the kidney. Best of luck!

What is the difference between an MRI and CT?

Two entirely different ways to look at the same area. The MRI uses magnets and takes a long time in an enclosed space, so if you have a pacemaker it won't be the best for you READ MORE
Two entirely different ways to look at the same area. The MRI uses magnets and takes a long time in an enclosed space, so if you have a pacemaker it won't be the best for you unless you have one that is MRI compatible. Also, if you are claustrophobic, can significantly impact the test. The CT uses radiation and is best to look for subtle fractures. Best thing to do is simply ask your doctor...sure he has good reasons! Best of luck!

What does an MRI angiography show?

MR angiography is an MRI, which uses magnetic fields rather than radiation, designed to look specifically at your blood vessels. It is generally used to look for any narrowings READ MORE
MR angiography is an MRI, which uses magnetic fields rather than radiation, designed to look specifically at your blood vessels. It is generally used to look for any narrowings in vessels, aneurysms (regions that are abnormally large), or damage to the vessels such as dissections, where part of the lining of the artery is torn. Hope this helps!

Is an MRI scan safe for children?

Yes. The benefit of an MRI over a CT is that there is no radiation involved. I hope your son feels better!

What is a lung PET scan?

A PET scan involves injection of a small amount of radioactive material that collects in regions of active metabolism. A lung PET is designed to see if there is active metabolism READ MORE
A PET scan involves injection of a small amount of radioactive material that collects in regions of active metabolism. A lung PET is designed to see if there is active metabolism in a mass within the lung. If so, that mass will need to be addressed further. Follow the preparations given by the imaging center. They are not too restrictive. Best of luck!

Why is a CT scan necessary for pneumonia?

In general, a CT scan is not necessary for this indication. Typically, just a chest X-ray will do. However, if he is worried about an atypical infection (walking pneumonia) or READ MORE
In general, a CT scan is not necessary for this indication. Typically, just a chest X-ray will do. However, if he is worried about an atypical infection (walking pneumonia) or other types of lung disease, a CT is better. Just ask your provider what's on his mind!

Is an MRI scan painful?

No, but it is loud, and if you have claustrophobia, it will not be pleasant for you as the tube is tight. Your technologist will provide you with ear protection but know in advance READ MORE
No, but it is loud, and if you have claustrophobia, it will not be pleasant for you as the tube is tight. Your technologist will provide you with ear protection but know in advance it is not a quiet procedure. Best of luck!

What are MRI results supposed to indicate?

That's actually a much larger question. Please consult with your ordering physician what they are interested in finding. Any radiological examination provides a tremendous amount READ MORE
That's actually a much larger question. Please consult with your ordering physician what they are interested in finding. Any radiological examination provides a tremendous amount of information, designed to aid referrings into making the best treatment choices, MRI included.

My son has been having bad headaches. His neurologist is sending him to a radiologist. What can we expect next?

Most likely the neurologist requested an MRI. Your son will be given a set of headphones to cover his ears and placed in a fairly tight tube. If he is claustrophobic he will READ MORE
Most likely the neurologist requested an MRI. Your son will be given a set of headphones to cover his ears and placed in a fairly tight tube. If he is claustrophobic he will not like the procedure, as his head will have to be in the tube. The scan actually takes around a half hour, and the test results will depend on his ability to hold still. Too much motion will cause blurring on the images, which will make interpretation difficult. That being said, the test will be over shortly and you will receive the results most likely within a day. good luck!

I accompanied my mother for her X-ray and I didn’t know I was pregnant then. What should I do?

The risk of radiation effects on a fetus for a back radiograph series on a person standing away from the patient is extremely, extremely low. You actually receive over twenty READ MORE
The risk of radiation effects on a fetus for a back radiograph series on a person standing away from the patient is extremely, extremely low. You actually receive over twenty times more background radiation from radon sources in your home than you will from that single medical exposure. So, rest assured and congratulations!

How can I ensure no other cancer cells are present in my body?

The best way to check for distant metastases is a separate scan called a PET-CT, which helps detect the presence of cancer cells throughout the body. Periodic surveillance will READ MORE
The best way to check for distant metastases is a separate scan called a PET-CT, which helps detect the presence of cancer cells throughout the body. Periodic surveillance will be necessary, so be sure to keep your appointments and follow the recommendations of your oncologist. Best of luck.


Sean L. Johnston, MD, PhD

What if I'm allergic to contrast?

Contrast allergies should always be taken seriously. While most people have a similar level of reaction, there are cases where a person with a minor allergy at one session had READ MORE
Contrast allergies should always be taken seriously. While most people have a similar level of reaction, there are cases where a person with a minor allergy at one session had a major reaction (as in airway compromise) at a later setting. If you need a CT with contrast in the future, you should ask your primary care physician to prescribe the pre-treatment protocol that is in place at your local hospital or imaging center. This usually involves a short course of steroids prior to the administration, which stops the allergic reaction from even starting.

Is pregnancy possible after chemotherapy?

It is possible, although much less likely, as chemotherapy tends to hamper fertility. Doesn't make it impossible, but your sister needs to know the odds are a bit against her READ MORE
It is possible, although much less likely, as chemotherapy tends to hamper fertility. Doesn't make it impossible, but your sister needs to know the odds are a bit against her at this point. Breast feeding will be fine, as the radiation does not cover the opposite breast. Best of luck!

Airport security and being pregnant

Hello- Yes, you may go through the scanner at the airport. The radiation dosage is so low that it doesn't pass through the skin, and therefore does not provide any significant READ MORE
Hello-


Yes, you may go through the scanner at the airport. The radiation dosage is so low that it doesn't pass through the skin, and therefore does not provide any significant increased risk to your fetus. Congratulations!


Sean L. Johnston, MD, PhD